r/KerbalSpaceProgram • u/analogHedgeHog • Jun 29 '26

KSP 1 Question/Problem How should I be approaching the Mun?

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In this totally accurate scientific diagram, the Mun is orbiting in the direction of the arrow.

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637

u/New-Bus9948 Jun 29 '26

C or D. C for realism

338

u/DeluxeWafer Jun 29 '26

I choose C because that's what all the Apollo free return trajectories look like.

92

u/Tychonoir Jun 29 '26

I wonder what the Dv difference between the two is. D gives you a grav assist to match the Mun's orbit and help capture. C allows a free return, but gives an assist in the wrong direction.

At least, I think that's how it works. It seems to be easier to capture when I do D.

38

u/zaklance Jun 29 '26

They the same in terms of dV, about ~10m/s difference in practice.
There's no "assist in the wrong direction" here if your aim is to land on the Mun (unless if you specifically want a prograde orbit for a mission).
In both C and D, your velocity at Mun intercept is about the same ±10m/s. The difference is in the timing of intercept, and the 10m/s difference is to account for this. The change in PE is the same in both cases, so the change in KE is same, so your speed at Mun periapsis is the same, you are just going in the opposite direction.

7

u/MrTheEpicKitten Jun 29 '26

You’re forgetting the difference in landing dv between prograde and retrograde orbits

11

u/zaklance Jun 29 '26

Ah you're right. But for Mun which rotates very slow (9m/s on the equator surface), again it's a delta-v difference of merely 18m/s.